// Write a hotel management program with given interface. 

// Each method (except constructor) should take fixed time (not dependent on hotel size).

using System;

using System.Diagnostics;

​

public class Program

{

    public static void Main(string[] args)

    {

        Hotel hotel = new Hotel(5);

        // test sequence: 0 means check-in, >0 means check-out

        foreach(int room in new int[]{ 0,0,0,0,0,4,2,0,0})

            Test(hotel, room);

    }

    public static void Test(Hotel hotel, int n)

    {

        if(n == 0)

        {   // test check in

            Console.WriteLine("Room {0} allocated", hotel.checkIn());

        }

        else

        {   // test check out

            hotel.checkOut(n);

            Console.WriteLine("Room {0} freed", n);

        }

    }

}

​

public class Hotel

{

    Queue freeRooms;

    // constructor to set number of rooms

    public Hotel(int totalNumberOfRooms)

    {

        freeRooms = new Queue(totalNumberOfRooms); 

​

        for (int i = 1; i <= totalNumberOfRooms; i++)   

            freeRooms.Push(i);

    }

​

    public bool hasRoomsAvailable()

    {

        return !freeRooms.IsEmpty();

    }

​

    // Before: hasRoomsAvailable

    public int checkIn()

    {

        Trace.Assert(hasRoomsAvailable());

        return freeRooms.Pop();

    }

​

    // Before: roomNumber is occupied

    public void checkOut(int roomNumber)

    {

        freeRooms.Push(roomNumber);

    }

}

​

public class Queue 

{

    // invariant: 

    // the array is considered as circular (next index after data.Length-1 is 0)

    // the queue contains count elements residing in data[head], data[head+1] etc

    private int[] data;     

    private int head = 0; 

    private int count = 0;

    public Queue(int size) 

    {

        data = new int[size];

    }

    public bool IsEmpty() 

    {

        return count == 0;

    }

    public bool IsFull() 

    {

        return count == data.Length;

    }

    public void Push(int v)

    {

        if (IsFull())

            throw new ApplicationException("Queue full");

​

        data[(head + count) % data.Length] = v;

        count++;

    }

    public int Pop()

    {

        if (IsEmpty())

           throw new ApplicationException("Queue empty");

​

        int v = data[head];

        head = (head + 1) % data.Length;

        count--;

        return v;

    }

}